Part of a protein found in breast milk could be used to wipe out certain types of bacteria, scientists have found.

The study, by the National Physical Laboratory (NPL) and University College London, found that the minuscule fragment, less than a nanometre in width, is responsible for giving the protein its anti-microbial properties.

This is what makes breast milk so important in protecting infants from diseases in their first months of life.

The protein, called lactoferrin, effectively kills bacteria, fungi and even viruses on contact.

After identifying the fragment, scientists re-engineered it into a virus-like capsule that can recognise and target specific bacteria and damage them on contact, but without affecting any surrounding human cells.

Hasan Alkassem, a student who worked on the project, said: "To monitor the activity of the capsules in real time we developed a high-speed measurement platform using atomic force microscopy.

"The challenge was not just to see the capsules, but to follow their attack on bacterial membranes. The result was striking: the capsules acted as projectiles porating the membranes with bullet speed and efficiency.

This, the team suggested, could help boost the fight against the growing issue of antibiotic resistance by serving as "delivery vehicles" for cures.

The capsules could even pave the way for treatments for previously incurable diseases such as sickle-cell disease, cystic fibrosis or Duchenne muscular dystrophy.

In an interview with The Times, Dame Sally Davies, chief medical officer for England, said more needs to be done by governments and experts to tackle the antibiotics issue.

She said: "We need on average 10 new antibiotics every decade. If others do not work with us, it's not something we can sort on our own.

"This is a global problem. I am optimistic about this. The science is crackable. It's doable."

Colin Garner, honorary professor of pharmacology at the University of York and head of the charity Antibiotic Research UK, said the situation was too urgent to wait for international consensus.

The pipeline of new drugs had dried up and the problem was on the brink of becoming "intractable", he told The Times.

"My heart sinks when I hear the term 'global initiative'. How long has it taken the world to come to a sort of consensus about climate change?" he said.

" The problem of antibiotic resistance will be at least as intractable because each nation takes a different view of what is required."

The NPL findings are reported in the Royal Society of Chemistry journal Chemical Science.